Purification of sulphonic acid products



solubility in water.

Patented June 16, 1942 PURIFICATION OF SULPHONIC ACID raonvc'rs Paul M.Goodloe, 2nd, Woodbury, NHL, assignor to Socony-Vacuum Oil Company,Incorporated, New York, N. Y., a corporation of New York 1 No Drawing.Application October 21, 1.938,- Serial No. 236,246 v Q'CIaimS. (Cl.260-504) This invention relates to a process for the sep- Most of theprocedures now practiced for the aration and purification of sulphonicacid prodpurification of mahogany sulphonic acid products and moreparticularly to the purification of nets are based upon the selectiveflocculation oi,

oil-soluble sulphonic acid products, such as the the sulphonates or thecorresponding acids from so-called "brown or "mahogany acids obtained 5a comparatively dilute solution of the crude mafrom petroleum oil orothermineral oil. terial by the addition to the solution of certain Whenpetroleum fractions are treated with reagents. For instance, Wolff, U.S. Patent No. sulphuric acid, especially with strong acid or 1,240,523adds 50% sulphuric acid to the solution oleum, mineral oil sulphonicacid compounds are of crude sulphonates thereby causing the freedformed. These mineral oil sulphonic acid comsulphonic acids to separateout as a flocculation pounds are of two distinct types, one of whichprecipitate and the water solution of inorganic is characterized by itsoil solubility and the other matter is decanted. A well-known procedurein is characterized by its water solubility. the prior art for causingthe flocculation of the In the usual practice for the preparation of Ysulphonates from aqueous media has been the these sulphonic acid bodies,the oil is treated I saturation of the solution with common salt. withstrong sulphuric acid or oleum either for re- Such a process leavesconsiderable salt in the finement oi the oil or specifically forproduction sulphonates so'obtained which must be removed of sulphonicbodies. The treatment may be carfor many purposes. ried out either inone stage or many stages, and It is an object of this invention toprovide an the resulting sludge is separated from the oil. efiicientprocess for the purification of maho The oil which has been freed ofsludge is then any sulphonic acid products from crude material treated,either before or after neutralization, with in which they are contained.Another object of water or an aqueous solution containing a watertheinvention is to provide an economical process soluble solvent such asalcohol or acetone in for the purification of mahogany sulphonic acidorder to remove the sulphonic acid products re-' products which yield ahighly refined product maining in the oil, and these products areresuitable for service in any of the uses to which covered from theaqueous extract either by saltmahogany acid products are put. Stillanother me out or distilling oii the aqueous solvent. object is toprovide a process for obtaining pur- The sulphonic acids thus recoveredfrom the oil ified mahogany acids of controllably difi'erent dephase arecommonly designated mahogany or grees of solubility in water and oilfrom the same "brown acids because of their color and are crudematerial. These and many other objects usually characterized by theirsolubility in oil will appear from the following description of my whichis much better-than their solubility in invention.

water. For convenience, this, class of sulphonic The invention is basedupon the discovery that acid products will be referred to hereinafter ascrude sulphonic acid products from any source mahogany sulphonic acids.containing mahogany sulphonic acid products The sludge separated fromthe above operaalong with various impurities, such as mineral tion, withor without neutralization, yields suloil, sulphuric acid andotherinorganic matter, ph n c c s f a different kind upon digestion may betreated to obtain highly purified mahogwith water. Because of theircolor, these acids 4 ny sulphonic acid products by first preparing areknown as green" acids and generally eX-= an essentiallyaqueoussolutioncontaining the hibit the property of relatively lowsolubility in crude product and, after removal of on if on comparedm)the mahogany acids and better sired, subjecting the-resultant aqueoussolution containing the crude product to a solvent ex- It is Wen knownthat crude sulphonic acid traction process which extracts themahog'anyof varying amounts such as mineral oil sulphuric The Present. r is to beclearly dlstm' acid, other morgnic matter, Various refine guished fromprocesses for extracting sulphonic ment processes tending to producesulphonic acid acids or sulphonates directly from a crude prodproductsfreer of impurities have been proposed uct by means f a ent, s nce insuch processes However, so fa as known, none f the Previ- I impuritiesare carried along with the sulphonates Ous wcrk on the urifi ation fsulphonic id into the extract. These procedures are decidedly productshas touched upon the novel process difierent from my pr e s o extractingoi my invention. Phonic acids or sulphonates from an aqueous solution,whereby the impurities remain in the aqueous solution. 1

The aqueous solution in which the crude sulphonic acid product isdissolved may comprise,

for instance, either (1) an essentially pure water,-

solution, or (2) an aqueous solution containing an organic water-solubleemulsion-breaking agent, or (3) an aqueous solution containing a strongelectrolyte, or (4) an aqueous solution containing both an organicwater-soluble emulsion-breaking agent and a strong electrolyte.

If an essentially pure water solution is used, the extraction solventmust not only be slightly soluble in pure water but must also possessemulsion breaking properties. on the other hand. thevextraction of puresulphonic acids or sulelectrolyte solutions), amyl alcohols, benzylalcohol, ethyl acetate, amyl acetate, diethyl ether,

phonates from an aqueous solution with organic solvents which inthemselves have little or no capacity for breaking oil-water emulsionsis not practical because these organic solvents are emulsified with thewater by the sulphonates present. It, however,;a third agent capable ofbreaking emulsions is added in a proportion of about 1 to 50%, usuallyabout 5 to 10%, the use of such organic solvents becomes teasible.-Typical water-soluble organic. emulsion-breaking.

agents which may be added to the water :are methyl alcohol, ethylalcohol, isopropyl alcohol, propyl alcohol. acetone, methyl ethylketone, propionic acid and methyl acetate. These emulsion-breakingagents, moreover, facilitate dissolution of the crude sulphonic productin the water, but amounts over about 50% should not be added as thesolubility of the organic extraction solvent is then increased to anundesirable amount. Since a great many of the extraction solventspossess at least a slight tendency to form emulsions, it is usuallypreferable or necessary to extract from an aqueous solution containingan emulsion-breaking agent, as, for instance, one of those abovementioned. The formation or emulsions may also be lessened bythepresence of certain polar compounds, for example, inorganic salts, acidsand alkalis, which are strongly polar. Furthermore, the use of thesestrong electrolytes decreases the solubility Like many other solventextraction Processes as, 101- example, that used in petroleum refining,there are numerous organic compounds oi! widely differentclassifications which will serve as suit- 'able solvent extractants inthe present process. Ingeneral, alcohols containing 4 to"? carbon atoms,certain ketones, aldehydes, organic acids and esters, also-containing!to 7 carbon atoms are operable. Moreover, various aromatic hydrocarbons,chlorinated hydrocarbons, etc., are

- operable. By way oi example, the following specific compounds whichare suitable extraction solvents for my process m g t be mentioned:benmethyl n-butyl ketone, butyraldehyde, and isovaleric acid. Itis to benoted that compounds such asbutyl, amyl,'and benzyl alcohols, ethyl andamyl acetate, methyl m-butyl ketone, bu- Y tyraldehyde, and isovalericacid possess emulsion-breaking properties and may be used to extractfrom even a relatively pure water solution. Further, when largequantities of electrolytes such as salt are added to the water solution,for instance, up. to saturation not only may the above relativelywater-insoluble compounds be used, but other organic solvents which arewatersoluble but only slightly soluble in strong electrolyte-solutionsmay be used. Typical specific examples or these latter compounds areiso-' propyl alcohol, methyl acetate, methyl ethyl ketone, and butylcellosolve. It is obvious, there fore, that in this process asin *otherextraction processes, the number and diversity of solvents that may beused defies any definite chemical classification. Such a classification,however, is believed unnecessary as it is felt the teaching that thesolvents are organic liquids having a relatively high solubility tormahogany sulphonic acid products and only a slight solubility in theparticular aqueous solution from which the mahogany acids are to beextracted sui'iiciently defines the solvents thatthe may be readilydetermined. In selecting solv nt extracting agents,

it is desirable to choose compounds which possess boiling pointssuiliciently low that they may be separatedirom the sulphonic acids orsulphonates by distillation. at ordinary pressures without danger ofdecomposing the sulphonic acids or sulphonates, Distillation undersubatmospheric pressures may be used, if desired.

In carrying out my process, crude sulphonates or sulphonic acidscomprising mahogany sulphonic acid products along with impurities arefirstdissolved .in a suitable aqueous solution. This aqueous solutioncontaining the crude prod? uct is then preferably. but not necessarily,made distinctly acid with a mineral acid, it not already so, in order toconvert sulphonates to sulphonic acids. After the aqueous-solutioncontaining the crude sulphonic acid products. is prepared, the firststep ot-the purification process comprises removal of oil. While oil isusually presentas an impurity, it is obvious that ii the crude productbeing treated does not contain oil or i! the use to which the purifiedsulphonic acid product is to be put does not require the absence oi oil,this oil removal step may be omitted.

Removal of oil may be accomplished in the main by allowing the solutionto, stand, whereby the'oil separates from the solution and is removed bysuitable means, such as decantatiom.

The aqueous solution may then be completely ireed of mineral oil bywashing, for example, with a light petroleum naphtha. The resultingoil-tree aqueous'solution is then ready to be treated in order to obtainthe, brown sulphonic This step e! the purification process is accomsene,toluene, xylene, nitrobenzene, Chlorex (beta beta dichlorodiethyllether), ethylene dichloride, dipentene or turpentine, diethylcar bonate, butyl alcohols (tertiary must be used with acid productsfree from other impurities, such as sulphuric acid, other inorganicmatter, etc.. which are dissolved in the aqueous solution.

plished by solvent extraction. I

Accordingly, the oil-free aqueous solution is treated with a suitablevolume oi .an extraction solvent which is relatively insoluble in theaqueous solution andwhichhasa'substantial solubility for mahoganysulphonichcids. The amount oi the extraction solvent added, as forexample phonic acid products to one layer and the other layer comprisingaqueous solution retainsthe dissolved inorganic matter, mineral acids,and other impurities. The extraction solvent layeris then removed andthe sulphonic acids therein neutralized with caustic. After filtrationand distillation of the solvent which may'then be reused, thesulphonates are obtained in a pure condition.

Moreover, by the present invention comparatively pure sulphonates may beeasily and cheaply produced from the crude emulsion of oil, water, andsulphonates obtained as a by-product in the acid refining of petroleumdistillates to produce turbine oils. For instance, when tertiary amylalcohol (20% by volume) is added to such a crude emulsion of oil, water;and sulphonates, and the whole mixed and allowed to stand, there areformed three layers, viz., oil on top, water on the bottom, and asolution of sulphonates in amyl alcohol in between. This sulphonatelayer may be separated and the solvent recovered by distillation.

The purified mahogany sulphonic acid products prepared in accordancewith my process have been found to be highly suitable for thepreparation of soluble oils for use in the textile industry and ascutting oils. Moreover, these. purified products may be used withadvantage in any of the many applications to which such products are nowput.

If the natureof the sulphonic acids render it desirable, the aqueoussolution may be neutralized or made alkaline before the extraction.Regardless of whether the aqueous solution of crude product is acid,neutral or alkaline, varying amounts of salt or other electrolyte may beadded before or coincident with the extraction.

An important feature of my 'invention'is the discovery that by thepresent process purified mahogany acids of controllably differentdegrees of solubility in water and oil may be produced from the samecrude material dependent upon thepH of the solution being extracted andthe presence or absence of electrolytes. Thus, from a givencrude'mixture of mahogany .sulphonates or sulphonic acids a product isobtained which vfrom which they are extracted orin direct pro? portionto the decrease in-pH value'and the addition of suitable electrolytes.Although the process is particularly directed to the purification ofmahogany petroleum sulphonic acids, it is to be clearly understood thatmy invention contemplates, and is applicable to,

a the treatment for purification of any. crude sulphonic acid productsobtained from mineral oils a benzene. I

tions without departing from the in generaland the like, as forinstance, the sulphonation product of alkylatednaphthalenes or Theinvention will be further illustrated bythe following specific examples.However, it is to be understood that the invention is not to berestricted thereby, since theremay be wide variainvention. 1

Example I trated solution of oil and sodium sulphonates shows a fairlyhigh degree of water solubility 7 the absence of added salt or otherelectrolyte, theproduct is slightly less soluble in water. -If theaqueous solution (3) is neutralized or made alka line and an electrolyteadded, the extraction produces a product of a still diflerent grade,characterized by being less soluble in water and more soluble in mineraloil then either of the products mentioned just above. When thesulphonates are extracted from a neutral medium (4) in the absence ofadded electrolytes, the product exhibits a relatively low solubility inwater and correspondingly higher solubility in oil than any of the otherproducts mentioned above. Accordingly, it may be seen that the watersolubility of the mahogany acids is increased and the oil solubilitydecreased in direct proportion to the and inorganic impurities is thendiluted withone-half its volume of alcohol (95%), acidified withsulphuric acid (98%) and allowed to settle. After separating from theoil, the alcoholic solution is extracted one or more times withonefourth volume of light naphtha each time, to removethe final tracesof oil. The oil-free alcoholic solution is then extracted withone-fourth volume of benzene and the aqueous alcoholic layer drawn oiland retained for alcohol recovery. The benzene solution of sulphonicacids is neutralized with 42 B. sodium hydroxide and filtered. Theresulting filtrate is then distilled on a water bath, yielding aproductcontaining about 33% water which, when dehydrated is an ambersolid that may be easily crushed between the fingers to dry powder. Thedehydrated prod-' uct analyzes:

Example II For comparison, some of the solution of oil and sodiumsulphonates obtained from the acid-stock in the same manner as outlinedin Example I is finished by the conventional salting out process.

After asmuch oil as would separate has been removed, the solution issaturated with common salt which causes the flocculation of theremaining oil and the sulphonates. This semi-solid madecrease in pHvalue of the aqueous solution product analyzes as follows:

terial is separated, heated to 200 F. and allowed to settle. A furtheramount of the brine solution and some of the sulphonates are removedfrom the bottom and discarded to free the material as much as possible.from the salt. The sulphonates'are then heated at 300 F. until thewater content has dropped to less than 5% The Per cent Water 4.5 AcidltyTrace Ash 6.5 Mineral oil 70.5 Ash (anhydrous, oil-freematerialcalculated) 26 While this latter material is satisfactory foruse in cutting oils. iais not as active for this purpose as the materialobtained by my benzene extracspirit of the tion process and it is notsuitable at all for textile oils.

I claim:

1. The process 01 purifying a crude petroleum mahogany sultonate productcontaining watersoluble impurities which comprises agitating said crudeproduct with an alkaline aqueous medium containing suillcient salt tosubstantially saturate the water in said medium and an organic solventhaving substantial solubility for-said sulphonates and not more thanslight solubility in a substantially saturated aqueous salt solution,permitting two phases to form comprising an aqueous salt phasecontaining said impurities and a solvent phase containing purifiedmahogany sulphonates, separating the solvent phase from the aqueous saltphase, and recovering the purified mahogany sulphonates from saidsolvent phase.

2. The process 01 purifying a crudepetroleum 20 mahogan sulphonateproduct containing oil and water soluble impurities which compriseswashing an aqueous solution of the crude product with light petroleumnaphtha to remove oil, converting the washed aqueous solution to a sub-.stantialiy saturated aqueous brine solution, ex-

tracting the oil-free brine solution while it is in an alkaline statewith about 20 to 50% of an organic solvent having a substantialsolubility for mahogany sulphonates and not more than slight solubilityin said brine solution, whereby two phases are formed comprising anaqueous brine phase containing said water-soluble impurities

